Crane attachment for tractors



NOV. 21, 1944. Ff P, LAWLER CRANE ATTACHMENT FORVTRACTORS Filed Nov. 11. 1943 2 Sheets-Sheet 1 INVENTOR FRANK P. LAWLER BY aaZf/gaf/mf/z,

A TTORNE YS Patented Nov. 21, 1944 CRANE'ATTACHMENT- Fon TaACToRs y Frank P. Lawler;r Chicago, Ill., assigner t'oService Supply Corporation, Philadelphia, Pa., a corporation of- Pennsylvania.

pplicaton November 11, 1943, Serial No. 509,929

5 Claims. (Cl. 212-8) This invention relates to a crane attachment i'or tractors and especially a crane which is adapted to be mounted lon a standard tractorv of the conventional wheel type.

The object of the invention is generally to im- 'proveand simplify the construction and operation ofstructures ofthis character; to provide afcrane structure which is adapted to be attached to a standard wheel tractor in such a manner that the crane frame automatically transmits all of its loads to the four supporting ground wheels through` three points of support only under all conditionsof loading and operation; to provide a wheeled crane structure in which the front orsteering wheels are adjacent theboom point and are mounted rigidly relative to the supporting crane wheels are mounted in such a manner as to permit their free oscillation relative to the crane frame, thus insuringy that -ithe crane unit will remain vautomatically supported upon its four wheels under all conditions of normal loading and operation regardless of unevenness of the ground over which it may be required to travel;

lto provide a wheeled crane structure whichis continuously supported on three points under all conditions of load and no load, and in which two of the three points of support are always located between the center of gravity of the crane unit and the suspended load; to provide a crane unit mounted on the four wheels and n inv which thek center of gravity and the center ofload always come on the same side of the sidewlse overturning axes; and further, to provide a crane ,structure giving the operator a maximum vision coupled with a minimum inter'-v ference from structural members as he enters or leaves the operating seat. f

The invention is shown by way of illustration in the accompanying drawings, in which:

Fig. 1 is' a plan view ofthe crane attachment complete, except with the operating seat shown removed for clarity;

Fig. 2 is a sectional elevation Aon line 2-2 of Fig. 1; f

y Fig. 3 is a cross section on line 3--3 of Figl 2, showing the position of the crane elements when all four wheels rest on a level plane;

Fig. 4 i's a cross section similar to Fig. 3 except with the tractor, its rear axle land wheels shownftilted relative to the frameas when the crane unit is supported on uneven ground; and

Fig.`5 is a diagrammatic view ofthe crane attachment and tractor unit.

Referring to the drawings in detail, and esframe, while the rear` pecially Figs. 1 and 2, A indicates in general a conventional four-wheel tractor in which the motor or engine, the transmission housing, and the iinal drive housing, together with the rear axle housing, are all mounted to form a rigid unit structure.

`Completely surrounding this structure isa rectangular shaped crane supporting frame which consists of two longitudinally extending side beams 5 and 6 which are connected by cross beams 1, 8, 8 and I0, of which the beams 1 and 8 form the rear and front ends respectively of the frame. A front axle- II ris rigidly secured tol fand supportsthe front end of the frame by means of gusset plates I2 welded or otherwise securedto opposite sides of the frame, and the axle in turn is supported by front wheels I4 pivoted in forks in the usual manner to permit steering.

Al hanger arm I5, pivoted on a pin- I6, secured to the cross beam 8, is secured to the front endyof the tractor unit and forms a pivotal support therefor. The rear end of the tractor unit is supported by rear driving 'wheels I1, while the rear` .end of the crane frame is ypivotally supported in an upwardly extending arm I8 which is secured as at I9 to the tractor unit. Thus, the front end of the crane frame is supported directly by the front wheels while the front end of the tractor unit is pivotally sup-- portedV by the frame. Conversely, the rear end of the tractor unit is supported by the two rear driving wheels, while the rear end of the crane frame is pivotally supported by the tractor unit.`

Thisis important, as a three-point support for the crane frame is thus provided with two points ofr support forward, and one point at the rear. This particular form of support will later be referred to. f

The rear pivot point is formed by a sleeve 20 extending through the cross beams 9 and I0. and the arm I8.

` removal by welding, or by means of a set screw 2|, as here shown, while the arm isiree to pivot aboutthe sleeve or vice versa-the sleeve and frame are free to pivot about the arm.

Secured to the rear end of the craneframe, and at each side thereof is an A frame. This frame consists of vertical members 22, and angularly disposed beams or structural members 23and they are connected at their upper ends by a crosswisev extending arcuate-shaped meniber 24. Alsol extending crosswise of the A frame. and secured therein, is a shaft 25, and journaled thereon are a pair of sheaves 26 and 28a. A

The. sleeve is secured against' x boom is also supported by the crane frame. This boom consists of two arms 21-21 which at their lower ends are pivoted to the crane frame as at 28-28. The upper ends of the boom arms converge and may be connected throughout a portion of their length by a lattice-work or cross members in the usual manner, and a boom point sheave 29 is Journaled in the usual way at the point or upper end of the boom.

A two-drum hoist is suitably mounted at the extreme rear end of the crane frame, and in actual practice a cable 30 from one drum leads over sheave 26 and is dead-ended at the peak of the boom as at 3|. A second cable 32 carried by the other drum leads over the sheave 26a and 29 to a sheave hook block 33, and is then dead-ended near the point of the boom as at 34. The two-drum hoist may be driven in any suitable manner, or as here shown through a power take-off shaft 35 on the tractor, and when one rum is driven, a load attached to the hook block sheave may be raised or lowered while operation of the second drum will raise or lower the boom. The sleeve 2n serves two functions; first; that of a pivotal support for the rear end of the frame, and secondly, that of a housing or passage through which the power take-01T shaft may be extended. The sleeve 20 and the pin I6 are in direct alignment with each other so as to permit free oscillation between the tractor unit and the crane frame, or vice versa, and as the power takeoli shaft is positioned Within the sleeve and cen-v trally thereof there would be no need of the universal couplings shown. Strains may, however, be encountered during certain load conditions which might cause suilicient bending to set up detrimental deflections; hence, the use of universal couplings.

Fig. illustrates diagrammatically the threepoint support obtained by the two front wheels and the rear pivot, or the sleeve 2|).` These three points of support are indicated at 40, 4| and 42. The center of gravity of the crane unit is indicated at 43. and the load to be raised at 44. The axis of sidewise overturning of the tractor and frame is indicated by the lines 45-45, 45u-45a, and the weight lever arm by the arrow 46. It should be noted that the two points o! support indicated at 4| and 42, or in other words the front wheels, are located between the center of gravity 43 and the load 44. This is very important as it provides maximum stability against sidewise overturning when the crane is picking up, supporting or transporting a load. Stability is further insured due to the fact that the center of gravity 43 Aand the load 44 will, during all normal operating conditions, remain in a position inside or centrally of the lines or axis of overturning indicated at 45-45, 45u-45a. In other words, sidewise overturning cannot take place until the center of gravity of the load is shifted to the outside of the axis of overturning.

From the foregoing, it should be apparent that a simple rigid frame and boom structure is provided, and that by attaching it to the tractor in the manner disclosed and described, the major forces produced when lifting or transporting a load will be directed to the forward supports 4| and 42 of the three-point support, and as the front axle and the wheels which represent the forward supports 4| and 42 may be made as heavy as desired, the unit as a Whole may be designed for almost any load capacity within the power range of the tractor motor and hoist employed.

It should further be obvious that when a load is being picked up that the center of gravity or the weight of the crane unit plus the load being picked up shifts forward from the point 43 and assumes a position close to the two front supports 4| and 42 when the load is nally lifted and is being transported; hence, the tractor unit proper is subjected to a minimum of load and strain as no load can be transmitted to the front end of the unit, and only a small portion, if any, to the rear end or pivot point 4U. The engine and transmission, or in other words the main mechanism of the tractor, is thus subjected to minimum strain and load incident to operation of the crane attachment, and long life and dependable operation are assured.

Maximum vhead-on stability is provided inherently by the construction of the unit, and as sidewise stability is insured by the two forward supporting wheels 4| and 42 (Fig. 5), the driver or operator can work in comparative safety, There is of course, some possibility of sidewise overturning of a crane of this type, particularly when operating on a slope or uneven ground surface: hence, it is important that the driver or operator should be able to jump clear of the machine without interference from either side. To this end it will be noted that the diagonal or structural members 23 of the A frames are kept Well behind the drivers seat and that the boom pivot points 28 are kept Well in front thereof. This arrangement provides a maximum of visibility, and at the same time leaves both sides of the unit open or free of obstructions so that the operator can quickly escape in case of emergency, overturning, etc.

comprising a rectangular shaped frame having a front and tion between the rear end of the tractor and the frame and supporting the rear end of the frame, said last-named pivotal connection forming a third point of support for the frame, a tw0-drum hoist supported by the frame, and a boom pivotally supported on the frame and operated by the hoist.

2. A crane structure of the character described comprising a rectangular shaped frame having a front and a rear end, an the front end of the frame, a pair of steering Wheels one on each end of the axle and forming a two-point support for the front end of the frame,

the front end of the tractor, a pivotal connection aseasn between the rear end of the tractor and the frame and supporting the rear end ot the frame, said last-named pivotal connection forming a third point of support for thevframe, a two-drum hoist supported by the frame, a boom plvotally supported on the frame and operated by the hoist, and means for transmitting power. from the tractor `to operate the hoist and boom.

3. A crane structure of the character described comprising a rectangular shaped frame having a front and rear end, an axle and a pair of steering wheels supporting the front end of the frame, a tractor disposed within the frame, driving i wheels on the tractor supporting the rear end of the tractor, a pivot onthe front end of the frame supporting the front end of the tractor, apivot on the rear end of the tractor supporting the rear end of the frame, said pivot forming a rear single point support and the front steering wheels a yand the front supports form the axes of sideways overturning of the tractor and frame with the weight or center of gravity of the tractor and frame located on a center line drawn through the rear support and centrally between the front supports, and a load carrying boom pivoted on the frame and positioned on -the same center line.

4. A crane structure of the character described comprising a rectangular shaped frame having a front and rear end, an axle and a pair of steering wheels supporting the front end oi.' the frame, a tractor disposed within the frame, driving wheels on the tractor supporting the rear end of the tractor, a pivot on the front end of the frame supporting the front end of the tractor, a pivot on the rear end of the tractor supporting the rear end of the frame, said pivot forming a rear single point support and the front steering wheels a pair of spaced front supports for the frame whereby lines drawn through the rear support and the front supports form the axes of sideways overturning of the tractor and frame with the weight orl center of gravity of the tractor and frame located on a centerline drawn x through the rear'support and centrally between the front supports, aA two-drum hoist support- 1 ed by the frame, and a boom piivotally supported by the frame and operated by the hoist. said boom being located on the same center 'une as the center of gravity of the tractor and frame,

5. A crane structure of the character described comprising a rectangular shaped frame having a front and rear end, an axle and a pair of steering wheels supporting the front end of the frame, a tractor disposed within the frame, driving wheels on the tractor supporting the rear end of the tractor, a pivot on the front end of the frame supporting the front end of the tractor, a pivot on the rear end of the tractor supporting the rear end of the frame, said pivot and the front wheels forming a three-point support for the frame, a hoist secured to the rear, end of the frame, a seatl for the operator of the tractor disposed forward of the hoist, a boom pivoted to the frame at a point forward of the drivers seat, a pair of A-shaped frames secured to the frame, one at each side thereof and to the rear of the drivers seat, guide sheaves carried by the A frames and cables extending from the hoist and over said guide sheaves to operate the boom, said A-shaped frames being spaced a suiiclent distance rearwardly of the drivers seat and the pivotal end of the boom being spaced sulciently forward of the drivers seat to permit unobstructed entrance of exit of the driver from the seat,

' FRANK P. LAWIJJRk 

